1. Field of the Invention
The present invention relates to an electrical insulator. More specifically, the invention relates to an electrical insulator wherein when the insulator is impacted with a projectile and a shed is broken, a crack does not extend to a head portion thereof. Thus, for example, no reduction in power supply or line drop occurs. Such an electrical insulator preferably consists essentially of alumina.
2. Related Art Statement
An example of a heretofore known ceramics suspension insulator is shown in FIG. 10. Typically, such an insulator has a thickness a of a head portion 51 which is to be covered with a cap approximately the same as the thickness b of a shed 52.
When the above conventional suspension insulator made of ceramic is used in power transmission lines and a projectile fired from, for example, a hunting gun impacts upon the shed, a crack extends not only to the shed but also to the head portion. In some cases, the suspension insulator is scatteringly broken so that the insulator will not fully perform its function. As a result, there occurs a drop of the power transmission line and interruption of the power supply results, which may cause unexpected serious disasters. Recently, such accidents have successively occurred particularly in North America, South America, Australia, etc., where high power projectiles are used in hunting.